[Problem] Opera dictionaries don't download.

I am trying to download a dictionary for Opera in the "spell check" section of the settings.
When I search for the language it says "The dictionary download has failed" or something similar, and further down it says something like "Check with your network administrator to make sure the firewall is not blocking downloads from the Opera servers".
It also shows a button that says "retry", but when you click it, nothing happens.

What can be done about it?. and if so, what configuration will I have to make of the firewall?.